Hi, I have a colour-colour (that is, V-R against B-V) diagram of a young open cluster, and I was wondering if anyone has any suggestions on any information that can be gleaned from such a diagram? I have searched the internet and these forums to no real avail. There is a clear linear line through the diagram with many stars on either side, perhaps there is a standard V-R/B-V correlation my observations can be compared against? Would it make sense to compare my diagram with that found from Landolt's data: http://brucegary.net/photometry/V-R.htm ? If anyone could help me begin to interpret the diagram, or provide me with a link to actual practical analysis I could utilise it would be much appreciated. Thanks.